Optical intensity adjustment devices

An optical intensity adjustment device for adjusting the intensity of optical radiation incident thereon comprising a first transparent conducting electrode, a second transparent conducting electrode, a layer of a twisted nematic liquid crystal material contained between said first electrode and said second electrode, an optical polarization polarizer located adjacent to said first electrode for linearly polarizing optical radiation incident on said layer via said first electrode, an optical polarization analyzer located adjacent to said second electrode for analyzing the plane of polarization of optical radiation emergent from said layer, means for applying a voltage between said first electrode and said second electrode and, electrically connected to said means for applying a voltage, photoelectric means for sampling and providing adjustment of the intensity of optical radiation falling on said device, said photoelectric means comprising a photoconductive layer formed from a multiplicity of islands of a photoconductive material so physically disposed with respect to said layer of liquid crystal material that when optical radiation is incident on a localized region of said device said radiation causes the electrical resistance of said photoconductive layer in said localized region to fall and consequently causing said voltage to be applied mainly across said layer of liquid crystal material in said localized region to adjust the plane of polarization of said radiation in said localized region and reduce the intensity transmitted by said analyzer in said localized region.